The invention relates to the field of telemetry systems for monitoring the physiological conditions of patients within a hospital environment.
Conventional telemetry systems for monitoring a number of patients have typically utilized a passive antenna, such as a conventional whip antenna, mounted on a receiver which displays the data received from the transmitters. Such systems are adepuate where all of the beds and ambulatory patients are confined in one area, such as an open ward.
Where the patients have been located in a number of rooms, a separate passive antenna, amplifier and power supply have been required at each location. This necessitates the installation of a large number of system components and creates added expense. Because the antennas cannot be connected in series, couplers are required for even a two-antenna system.
Conventional passive antennas utilized in a multi-patient monitoring system must be of substantial length for adequate reception. For example, a typical whip antenna is ordinarily extended about 18 to 36 inches. It is desirable to minimize the space occupied by telemetry systems, and passive antennas are not adaptable to provide good reception unless extended to a significant height.
Passive antennas also have the disadvantage of causing false alarms in the monitoring system as their signal/noise ratio is not always sufficiently high.
Small active antennas including passive reception elements and a signal amplifier in one integrated unit have not been used to advantage in a hospital environment, nor has a combiner been incorporated to allow series cascading of antennas.